docs: def merge_models(self, store_in_memory=False, outdir=None, outname=None, force_rerun=False):
          """Merge all existing models into a Structure's first_model attribute.
  
          This directly modifies the Biopython Structure object. Chains IDs will start from A and increment for each new
          chain (which is a Model that is converted).
  
          Args:
              store_in_memory (bool): If the modified Biopython Structure object should be stored in the attribute
                  ``structure``
              outdir (str): If ``store_in_memory`` is False, the structure file has to be written somewhere so an output
                  directory must be specified here
              outname (str): If ``store_in_memory`` is False, the structure file has to be written somewhere so an output
                  filename must be specified here (i.e. 4BXI_bio1)
              force_rerun (bool): If merged file should be overwritten if it already exists
  
          """
  
          if store_in_memory:
              if self.structure:
                  parsed = copy(self.structure)
              else:
                  parsed = self.parse_structure()
              self.structure = merge_all_models_into_first_model(parsed)
          else:
              new_structure_path = write_merged_bioassembly(inpath=self.structure_path,
                                                            outdir=outdir, outname=outname,
                                                            force_rerun=force_rerun)
              self.load_structure_path(new_structure_path, file_type='pdb')